Various articles, such as protective articles and support articles are typically fabricated at least in part from polymeric materials. Protective articles, such as helmets, safety lenses, and protective housings, and support articles, such as beams can be subjected to stresses and/or impacts that result in damage to the article, which could lead to catastrophic failure of the article at a point in time after the damage occurred. In some instances, the occurrence or presence of such damage is not accompanied by a visually observable indication thereof in the article. In the absence of a visually observable indication of the damage, the damaged article would not likely be withdrawn from use, and an unexpected catastrophic failure of the article could occur.
Mechanochromic materials change color in response to a change in mechanical stress, such as impacts. It is known that mechanochromic materials can be incorporated into certain articles so as to provide a visual indication that the article has undergone a threshold mechanical stress event, which could result in catastrophic failure thereof. Some mechanochromic materials can undergo a reduction in stability over time, which can result in reduced mechanochromic properties. A reduction in mechanochromic properties can be accompanied by an undesirable reduction in a visually observable indication that the article in question has undergone a threshold mechanical stress event.
It would be desirable to develop new mechanochromic materials that can be used to provide a visually observable indication that an article, which incorporates such mechanochromic materials, has undergone a threshold mechanical stress event. It would be additionally desirable that such newly developed mechanochromic materials posses improved stability.